Indicted by a federal grand jury in Chicago in 2014, the 50-year-old Firtash is painted in court papers as a regular Bond villain, accused of masterminding an international titanium-mining racket. With references to Swiss bank accounts, bribes for corrupt Indian politicians and links to Chicago-based airplane manufacturer Boeing, the case reads like a spy thriller.

Efforts to extradite him from Austria, however, have been unsuccessful. Freed on an enormous $174 million bond that highlighted his enormous wealth, Firtash last year convinced a lower court Austrian judge that the case was a politically motivated attempt by the U.S. to clamp down on allies of Russian President Vladimir Putin following the Russian annexation of Crimea.

With close ties to the Kremlin — and a history of supporting anti-Western forces in Ukrainian politics — Firtash had grounds to make his case. He maintains his innocence.

But the U.S. Department of Justice hasn't given up. It has pushed the Austrian Ministry of Justice to appeal to a higher court the decision not to extradite Firtash, an appeal that is still pending.

That prompts an intriguing question for the Trump campaign: Would a Trump administration aggressively pursue Firtash's extradition, or might it be tempted to quietly end the U.S. pursuit of a former business partner of Trump's campaign manager?

Manafort and the Trump campaign did not respond Monday morning to requests for comment.

But Manafort's ties to Firtash are extensively documented in court filings from an unrelated federal case in New York.

Manafort and business partners, including Firtash, in 2008 negotiated an $895 million deal to buy the site of the Drake Hotel in Manhattan, which they hoped to redevelop as a luxury mall and spa called Bulgari Tower. Memos of meetings that Manafort and Firtash attended in Kiev are included in the lawsuit, though the deal eventually fell apart.

While Firtash had yet to be indicted at that point, a diplomatic cable sent by U.S. ambassador to Ukraine William B. Taylor during the period in which Manafort and Firtash were negotiating, later leaked by Wikileaks, alleged Firtash had ties to Russian organized crime and described him as "one of Ukraine's most wealthy and notorious oligarchs."

Manafort's extensive ties to pro-Russian former President Ukrainian Viktor F. Yanukovych and to Ukrainian business leaders sympathetic to Moscow have become an issue in the presidential campaign, thanks to Trump's frequent statements of admiration for Putin, who Trump has described as "strong leader."

Trump told ABC host George Stephanopoulos in an interview that aired Sunday that he had no involvement in removing a provision from the Republican platform that would have called on his administration to arm Ukraine to defend itself against Russia.

Should Firtash ever be brought to Chicago to stand trial, his ties to Manafort may add to the intrigue.